In most cases, immuno-deficient patients such as cancer patients undergoing chemotherapy, transplant recipients, AIDS patients, etc. are concerned about fungal infections which are caused by opportunistic pathogens such as Candida spp., Aspergillus spp. and Cryptococcus neoformans. Commercially available anti-fungal agents in current use, however, suffer from the disadvantage of being toxic and showing inhibitory activity against only a narrow spectrum of fungi. With the recent progression of an increase in the population of immune-deficient patients, there has been an increasing demand on antifungal agents that can inhibit a wide spectrum of fungi and exhibit excellent pharmacokinetic properties. To meet the demand, a variety of antifungal compounds therapeutic for fungus-infected mammals including humans are under development and study.
Triazole derivatives which can be orally administered were reported as antifungal agents used for the treatment or prevention of fungal infections in the late 1980s. Representative examples include fluconazole consisting of 5-membered rings (UK Patent No. 2099818), and itraconazole (U.S. Pat. No. 4,267,179). In addition, triazole compounds with hetero ring substituents are disclosed in European patent No. 440372 characterized by the 6-membered pyrimidine voriconazole, in European Patent No. 241232 (Shionogi Co.) characterized by the five-membered ring isoxazole, and in European Patent No. 659751 (Takeda Co.) characterized by triazolone. Further, U.S. Pat. No. 5,716,969 (Kaken), US Patent Publication No. 2009/0299071 (Fujifilm Fine-chemicals Co.), Bioorganic Medicinal Chemistry Letter 201020 2942-2945) and Archiv der Pharmazie 2009342: 732-739 (Second Military Medical University) discloses piperidine, and WO 01/89447 (Second Military Medical University) discloses triazole derivatives with piperidine rings.
However, these conventional compounds are not sufficient as medications in terms of antifungal activity against some pathogenic opportunistic fungi which occasionally cause fatal infections in immune suppressed patients, in terms of safety and in terms of in vivo pharmacokinetics. Therefore, there is a need for compounds that are higher in biosafety and which have greater in vivo absorptivity and have more potential antifungal activity as therapeutics of mycosis.